Down syndrome » General
Q90.9

Definition:

A congenital chromosomal malformation syndrome characterized by a well known pattern of minor and major anomalies and associated with excess chromosomal 21 material. Incl. trisomy mosaicism and translocations of chromosome 21.

Notes:
Doctors and nurse neonatologist, as they know about the normal variations, can easily recognize a newborn with Down syndrome.
The syndrome due to a chromosomal anomaly that has clinical diagnosis even without karyotype is Down syndrome [Q90.9]. All the others (Edwards, Patau, Turner, cri-du-chat, etc.) can be diagnosed only after citogenetic testing.
Bear in mind that Down, Patau, Edwards, cri-du-chat, Turner, etc, are clinical diagnoses, somewhat trisomy 21, 18, 13, etc, are laboratory diagnoses.
Trisomy 21 NOS is coded in Q90.9, as Down syndrome NOS, or unspecified.
The chromosomal anomalies NOS, or unspecified are coded in Q99.9.